Synthesis of 5,10-Secosteroids and their evaluation as selective inhibitors of steroid-transforming enzymes. These compounds are designed as inhibitors of delta 5-3-ketosteroid isomerase, of 3- and (3 and 17) beta-hydroxysteroid dehydrogenases, and of procedures involved in the oxidative degradation of lanosterol and of cholesterol. The mechanisms by which enzyme inhibition occurs will be studied. BIBLIOGRAPHIC REFERENCES: Batzold, F. H. and C. H. Robinson. Synthesis of beta gamma-Acetylenic-3-Oxosteroids of the 5,10-Seco Series. J. Org. Chem., 41, 313-316, 1976. Batzold, F. H., A. M. Benson, D. F. Covey, C. H. Robinson and P. Talalay. The delta 5-3-Ketosteroid Isomerase Reaction: Catalytic Mechanism, Specificity and inhibition. Advances in Enzyme Regulation, Vol. 14, G. Weber, Ed., Pergamon Press, Oxford, 1976, p. 243-267.